This invention represents the inventor's ongoing efforts in the field of large scale refrigeration systems.
It is desirable to be able to reduce the heat generated by high-power three-phase motors used for air circulation in large industrial refrigerators and freezers. Excess heat generated by these motors must be removed from the cooled chamber by the chamber refrigeration system. Reducing the generated heat causes the system to operate less often, thus saving energy and reducing the cost of operating the refrigerator or freezer. Such reduction of motor heat has proven to be effective in saving energy and cost of operation in smaller, single-phase powered walk-in refrigerators and freezers, such as those in restaurants and convenience stores.
Prior art methods of reducing motor-generated heat in three-phase motors include complicated, high power systems that either control the frequency of the applied power or divide the applied power into short pulses. These systems are very expensive, very difficult to install, and require, in some circumstances, replacement of the standard motors with special motors using high voltage insulation. In addition, the existing three-phase control systems generate large amounts of heat in the performance of their control function, often greater than the amount of motor heat that they save.
The following prior art reflects the state of the art of which applicant is aware and is included herewith to discharge applicant's acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed.
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